Electrical measuring instrument



March 14, 1939.

F. x. LAMB 2,150,836

ELECTRI CAL MEASURING INSTRUMENT Filed Feb. 27, v 1937 Patented Mar. 14, 1939 I 2,150,836

UNITED STATES PATENT OFFICE ELECTRICAL MEASURING INSTRUMENT Francis Lamb, East Orange, N. J., assignmto Weston Electrical Instrument Corporation, Newark, N. J., a corporation or, New Jersey Application February 27, 1937, Serial No. 128,268 4 Claims. (G11. i3l5l) This invention relates to electrical measuring the inner end is secured to a base d of molded instruments and more particularly to electrical plastic material, such as phenolic resin, which measuring instruments having illuminated scale supports a permanent magnet 5 and a. moving plates. 7 system that includes a pointer 6 that is displace- 5 It has been the practice to provide a direct"'-able .over a graduated scale plate'l. The terillumination of the scale plates by lights placed minals 8 and the posts 9 that carry the scale plate on the front of a panel board, or an indirect ill are secured to or molded into the base 4 in the lumiuation by small lights placed within the inusual manner. strument casing. The direct illumination method This illustration of the instrument parts will 10 may be used whether the instruments are of be recognized as typical of small panel-mount-- m large or or" small size, but the recent trend'toing types of instruments now in general use. The Wards small size instruments has made it im= interior of the casing l is substantially completely possible to place a light bulb within the instrufilled by the measuring instrument and it is not ment casing. It has been proposed to replace Practical to losate a Smell lamp bulb within h a section of the instrument casing by a glass casing o illum m e scale plate. window and to place lamp bulb back of the In accordance with this inventio the in i panel to obtain an indirect illumination of the is formed of a transparent organo-plastic matescale plate, but this adds to the expense f man'urial such as a vinyl resin, cellulose acetate or the facture and, by increasing thenumber ot parts, t y 'li a Building material 801d 0 increases the possibility that dirt and moisture mercially under trdfle-merkhucite4 A g t 20 may enter the instrument casing, source at the rear of the panel, such as the small An object of this invention is to provide n lamp bulb to at the exterior of and adjacent the electrical measuring instrument having a unicasing will therefore light the p te 5 d tary casing that permits an indirect illumination s a p at l y d t illumination. A paqu of the scale plate by a light located outside the e a el coa ii is preferably p y d upo e 25 casing. An object is to provide a d m-1 ,1 outer end of the casing l and its mounting flange measuring instrument having a transpar t '2, to simulate the appearance of the conventional molded casing for admitting'light to the scale instrument casings r ed o a opaq e molded plate. More specifically, an object of this invention is to provide an electrical measuring instru- In the embodiment f the invention which is 30 ment of the flush mounting type which has a illustrated in Fig. 4, the entire instrument casing transparent casing of molded material for admitis formed of a transparent P the C g ting light to the interior of the casing, and an eluding base cylindrical Section l2 11 11 opaque enamel coating n portions of t casing ing the instrument proper, a sectorial enlargeto simulate the conventional instrument casings ment l3 extending above the cylindrical S on 35 of molded plastics. to house the translucent scale plate M, and a.

These and other objects and advantages of the cover I5 which completes the instrument usi invention will be apparent from the following The cover section has ewindow o i provided specification when taken with the accompanying with 8 glass Plate through which e po nter 46 drawing in which: and scale plate may be viewed-and the entire Fig. l is a front elevation of an embodiment of cover l5 and the cylindrical section I! may be the invention; covered with an opaque enamel H. The rear face Fig. 2 is a fragmentary vertical section through of the extension 01194111985? that p r ion which a panel having mounted thereon an instrument alines with the Scale Plate is uncoated o Pass shown in side elevation; instrument scale plate It. The instrument point- Fig.3is an enlarged fragmentary sectional view I5 is Opaque and its p ent 1 118 the of the instrument casing of Figs, 1 a d 2; d translucent scale plate I is easily. read with this Fig. 4 is a side elevation, with parts in e tion, indirect illumination of the scale plate from a 50 of another embodiment of the invention. lig t Source the 61 the Panel and 50 In the drawing, the reference numeral l ideneri r t h in r ca tines a molded cylindrical instrument casing hav- In trument casings of the typ c b pl y ing an integral flange 2 which adapts the instruthis invention are not expensive to manufacture, ment for flush mounting on a panel P. The outer provide adequfi- Protection against i and 111018- end of the casing carries the cover glass 3, and turn. and permit the indirect illumination of the 45 such as shown in Fig. 1, the instrument being li ht from a lam N a the rear of a panel to the 45 scale plates of one or more small instruments from a light source at the rear of an instrument panel.

It is to be understood that the invention is not restricted to the specific embodiments herein described and that there is considerable latitude in the design and construction of electrical measuring instruments that fall within the spirit of my invention as set forth in the following claims.

I claim:

1. A measuring instrument comprising an instrument movement including a pointer movable over a scale plate, and a casing for housing said instrument movement, said casing including an opaque flange for the hush mounting of the casing on a panel and a cylindrical section of a transparent organo-plastic surrounding the scale plate, whereby said scale plate may be illuminated by a light source exterior to said casing.

2. An electrical measuring instrument comprising an instrument movement supported on a base and including a pointer movable over a scale plate, a casing formed 01' a transparent organeplastic material housing said instrument movement, means for mounting said casing on a panel and with portions thereof at opposite sides 01' the panel, and an opaque coating upon said portion of the casing which will lie in front of a panel upon which the casing is mounted.

3. An instrument as claimed in claim 2, wherein said casing comprises a flanged cylindrical section secured to a base on which the instrument movement is mounted, the flange of said cylindrical section having the opaque coating thereon and being adapted to seat upon the panel for the flush mounting of the casing thereon.

4. An instrument as claimed in claim 2, wherein said scale plate is translucent, and said casing comprises a main section comprising a cylindrical portion havinga sectorial extension housing said scale plate and a cover section, said opaque coating extending over said cover section 20 and thecylindrical portion of said main section.

FRANCIS K. LAMB. 

